With improvement of functions of cameras of mobile phones, more users choose to use cameras of mobile phones to capture pictures. In a photographing process, how to rapidly and accurately locate a needed object is the main factor affecting user experience.
A lens zooming technology refers to changing a size, in a captured image, of a target object in a lens in a manner such as changing a focal length of the lens. Zooming manners are classified into optical zoom and digital zoom. The optical zoom is generated due to location changes of three parties, namely, a lens, an object, and a focal point. The digital zoom is to increase each pixel area in a picture by using a processor in a portable electronic device, to achieve an objective of zooming in. The portable electronic device may be a mobile terminal having a camera, a digital camera, or the like. The optical zoom is generally applied to a conventional zoom camera. A user manually changes a focal length by manually rotating a zoom ring on a lens cone. The digital zoom is mainly applied to a mobile terminal or an ordinary digital camera. A user changes a focal length by using an operating knob on a device body or by sliding on a screen with a finger.
In all existing lens zooming methods, a user needs to manually change a focal length. The user may need to perform adjustment for multiple times to reach a proper focal length. The operation is inconvenient.